Linux-Fan wrote: > I think the arguments of the RAID5/6 critics summarized were as follows: > > * Running in a RAID level that is 5 or 6 degrades performance while > a disk is offline significantly. RAID 10 keeps most of its speed and > RAID 1 only degrades slightly for most use cases. > > * During restore, RAID5 and 6 are known to degrade performance more compared > to restoring one of the other RAID levels.
* RAID 5 and 6 restoration incurs additional stress on the other disks in the RAID which makes it more likely that one of them will fail. The advantage of RAID 6 is that it can then recover from that... * RAID 10 gets you better read performance in terms of both throughput and IOPS relative to the same number of disks in RAID 5 or 6. Most disk activity is reading. > * Disk space has become so cheap that the savings of RAID5 may > no longer rectify the performance and reliability degradation > compared to RAID1 or 10. I think that's a case-by-base basis. Every situation is different, and should be assessed for cost, reliability and performance concerns. > All of these arguments come from a “server” point of view where it is > assumed that > > (1) You win something by running the server so you can actually > tell that there is an economic value in it. This allows for > arguments like “storage is cheap” which may not be the case at > all if you are using up some thightly limited private budget. > > (2) Uptime and delivering the service is paramount. Hence there > are some considerations regarding the online performance of > the server while the RAID is degraded and while it is restoring. > If you are fine to take your machine offline or accept degraded > performance for prolonged times then this does not apply of > course. If you do not value the uptime making actual (even > scheduled) copies of the data may be recommendable over > using a RAID because such schemes may (among other advantages) > protect you from accidental file deletions, too. Even in household situations, knowing that you could have traded $100 last year for a working computer right now is an incentive to set up disk mirroring. If you're storing lots of data that other people in the household depend on, that might factor in to your decisions, too. Everybody has a budget. Some have big budgets, and some have small. The power of open source software is that we can make opportunities open to people with small budgets that are otherwise reserved for people with big budgets. Most of the computers in my house have one disk. If I value any data on that disk, I back it up to the server, which has 4 4TB disks in ZFS RAID10. If a disk fails in that, I know I can survive that and replace it within 24 hours for a reasonable amount of money -- rather more reasonable in the last few months. > > Is anyone still using ext4? I'm not saying it's bad or anything, it > > only seems that it has gone out of fashion. > > IIRC its still Debian's default. Its my file system of choice unless I have > very specific reasons against it. I have never seen it fail outside of > hardware issues. Performance of ext4 is quite acceptable out of the box. > E.g. it seems to be slightly faster than ZFS for my use cases. Almost every > Linux live system can read it. There are no problematic licensing or > stability issues whatsoever. By its popularity its probably one of the most > widely-deployed Linux file systems which may enhance the chance that > whatever problem you incur with ext4 someone else has had before... All excellent reasons to use ext4. -dsr-
